By Abigail M. Obenchain, Ontario Ministry of Natural Resources’ Ontario Forest Research Institute.  This post is an addendum to Carrie Pike’s October 2011 article on white pine blister rust research in Minnesota.

November 2011: The fungal disease known as blister rust continues to vex those trying to regenerate eastern white pine (Pinus strobus). Where the risk of blister rust infection is high, nothing seems to protect the regenerating pine, not changes in silvicultural practices or even a warming climate.

Adding to the challenge of regenerating this tree species is its near-total lack of resistance to blister rust, an invasive alien pathogen that hopped the Atlantic early last century. In western North America, researchers working on sugar and western white pine have found genetic lines that can resist the disease. No such luck for researchers working on eastern white pine, despite decades of trying, both in Ontario as well as other parts of northeastern North America.

However, research geneticist Pengxin Lu and his crew at the Ontario Forest Research Institute (OFRI), part of the Ministry of Natural Resources, are following a promising alternate path: They’ve developed eastern white pine hybrids that can resist blister rust. So how’d they do that?

1. Using traditional breeding techniques in OFRI’s growth facilities, they bred eastern white pine with Eurasian pines, infected the new generation of young trees with the blister rust fungus, and screened the trees to see which ones survived.
2. They then backcrossed those surviving trees with eastern white pine for three more generations, each time resulting in trees that have more eastern white pine genes and fewer Eurasian pine genes. Again they infected the trees and screened them for resistance.
3. They now have a third generation hybrid backcross, with the newest generation nearly 94% eastern white pine yet able to resist blister rust.

“Field tests of eastern white pine hybrid backcrosses have indicated good growth rates and comparable wood attributes in areas where they have adapted well, particularly in southern and eastern Ontario,” Lu says.

Another promising development in producing blister rust resistant white pine at OFRI has been the opening of a new somatic embryogenesis lab. Somatic embryogenesis allows researchers to produce many genetically identical seedlings from a clump of embryonic tissue generated from a single tree seed embryo. Even more remarkable, these clumps can be stored indefinitely, for 30 years or more, in liquid nitrogen, for use over time.

“When you are producing seedlings from seed from seed orchards, you cannot be sure they will all be resistant; sexual reproduction can result in considerable genetic variation,” Lu explains. “Seedlings we produce using somatic embryogenesis, however, are propagated vegetatively, making them genetically unchanged, so we know they are resistant.”

Now that OFRI researchers have a somatic embryogenesis lab, large scale production of resistant hybrids for operational planting in Ontario is a distinct possibility.

Lu concludes, “With continuing research and development to make the next generation of hybrid backcrosses even closer genetically to eastern white pine, as well as have improved adaptation, growth, and genetic diversity, we will have a viable option for restoring white pine in high hazard areas where it has disappeared or significantly declined.”

For more information about eastern white pine blister rust research at OFRI, contact Pengxin Lu.